Saturday, June 23, 2018

The answer, my friends, is blowing in the tapetum lucidum

Here's an old verse you probably remember from childhood days:

Roses are red,
Violets are blue,
Sugar is sweet,
And so are you.


As valley girls everywhere used to say, gag me with a spoon.

Well, roses may be red and violets may indeed be blue (actually, I thought they were purple), but it is also true that humans are red and doggies are green.

Don't be confused, folks, I just changed horses in midstream. I'm referring to eyes in photographs:


Son of a gun.

I brought up the question a couple of posts back and a comment by our Scottish friend Adrian Ward to the effect that the eyes of some animals have a reflective layer behind the iris inspired me to do some research.

I found this:

"In dogs (and many other animals, but not people), the retina has a reflective layer behind it called the tapetum lucidum, which acts like a mirror, reflecting light at the back of the eyes. The reflective layer is what helps dogs see better at night. Light is reflected outward, giving the dog's retina a second chance to absorb the rays."

...and this:

"Short answer: In humans it is basically the red choroid plexus in the back of the eye you are seeing on a flashed photo, while it is the green-reflecting tapetum lucidum in dogs."

The red-eye effect in humans was explained nicely by Yale Scientific Magazine:

"The human eye can effectively adjust to different light conditions, but this adaptation is also what leads to the red-eye effect. The eye regulates the amount of entering light by contracting or expanding the pupil. At night, your pupils will accordingly enlarge to extract more light from their surroundings. However, this dilation also leaves your eyes unprepared for the sudden burst of light from a camera flash.

"When light from the flash enters your eyes under these conditions, your pupils are unable to contract fast enough (full constriction takes a few seconds) to prevent the light from reflecting back, off of the red blood vessels of the choroid. The choroid plexus nourishes the retina, and therefore contains ample blood supply. As a result, the camera will pick up the red reflection, resulting in the red-eye effect. Interestingly, due to their increased “dark adaptation,” children more commonly have red eyes in photographs.

"The amount of melanin, a light-absorbing pigment in the eye, also has a role in the red-eye effect. Individuals with lower levels of melanin will absorb less and thus reflect more light, explaining the high incidence of the red-eye effect in albinos.

"Though the cause of this effect is wired in the biology of the eye, some cameras can reduce red-eye by sending a few preliminary flashes before the final flash to give the pupils enough time to contract and adapt to the increased-light conditions. Another way to reduce the effect is to avoid looking directly into the camera lens, which will reduce the reflection of light. Finally, if all else fails, modern image editing software, such as Photoshop, can remove the red discoloration.

"With regard to why dogs and other animals may not have red-eyes but other colors, some animal species have a tapetum lucidum, which is situated in front of the choroid and reflects light back onto the retina thereby increasing light sensitivity. In dogs it is green. The following figure from Pets.SE shows the anatomy and the position of the tapetum in front of the choroid.


"Hence, the reason why animals with a tapetum lucidum have another eye color is that light does not reach the choroid in these species, giving rise to green-eye effects in dogs and cats."

...and finally, deep in wikipedia's article on the tapetum lucidum, in a subsection entitled "Eyeshine", I found this:

"Eyeshine is a visible effect of the tapetum lucidum. When light shines into the eye of an animal having a tapetum lucidum, the pupil appears to glow. Eyeshine can be seen in many animals, in nature and in flash photographs. In low light, a hand-held flashlight is sufficient to produce eyeshine that is highly visible to humans (despite our inferior night vision). Eyeshine occurs in a wide variety of colors including white, blue, green, yellow, pink and red (emphasis mine). However, since eyeshine is a type of iridescence, the color varies with the angle at which it is seen and the minerals which make up the reflective tapetum-lucidum crystals.

"White eyeshine occurs in many fish, especially walleye; blue eyeshine occurs in many mammals such as horses; green eyeshine occurs in mammals such as cats, dogs, and raccoons; and red eyeshine occurs in coyote, rodents, opossums and birds (emphasis mine).

"Although human eyes lack a tapetum lucidum, they still exhibit a weak reflection from the fundus, as can be seen in photography with the red-eye effect and with near-infrared eyeshine. Another effect in humans and other animals that may resemble eyeshine is leukocoria, which is a white shine indicative of abnormalities such as cataracts and cancers."

Folks, if you want any more information on this subject, I encourage you to look it up for yourself.

Friday, June 22, 2018

Progress is relative, or Civilization may not be the answer

I thought I-75 in Atlanta was bad but the Katy Freeway in Houston, Texas, is mind-boggling. The photograph was taken in 2015. At Thanksgiving we often sing "We gather together to ask the Lord's blessing" but this is a bit too much togetherness, in my opinion.

Yorkshire Pudding's peak district is looking better all the time.


Wednesday, June 20, 2018

Everything you ever wanted to know about the summer solstice but were afraid to ask

Here it is again, good old June 20th.

To spare myself time and effort, I hereby request that you go over to the sidebar on the right side of this blog, scroll down to all the way to the letter S section, and click on the words:

summer solstice

which will bring up for your viewing pleasure four infinitely fascinating posts about, you guessed it, the summer solstice, which is an unfortunate way of referring to it if you happen to live in the southern hemisphere where today is the first day of winter (kylie and sue, I'm looking at you, and also carol in Cairns in Far North Queensland, if you're still around, and maybe even Helsie in Brisbane).

If you are tempted not to go to all the bother, I would remind my longtime readers that by so doing you may get to see Paul Newman without his shirt on.

Read all the comments too as they're always fun.

I have to rest now. It's too hot to do anything else.

Tuesday, June 19, 2018

View from the bottom of the barrel by one who has been there

Hard on the heels of a powerful poem from Elizabeth, this morning I want to share with you "Twenty Years Ago", a powerful post from another cyberfriend in England, a man named Gary Pennick who blogs under the name klahanie. I'm sure it required courage both to write and to publish.

After you have looked at that, I have an off-the-subject question that I hope someone can answer. Why is it, when looking into a camera, that human eyes show red but doggie eyes show green?

This is neither a joke nor a trick question. I would really like to know the answer.

Monday, June 18, 2018

Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven

My English cyberfriend and Methodist clergywoman Elizabeth Stanforth-Sharpe posted a moving poem online today. It deserves re-posting without further comment from me.


The Day The War Came
by Nicola Davies


The day war came there were flowers on the window sill
and my father sang my baby brother back to sleep.
My mother made my breakfast, kissed my nose
and walked with me to school.

That morning I learned about volcanoes, I sang a song about how tadpoles turn at last to frogs.
I made a picture of myself with wings.
Then, just after lunch, while I watched a cloud shaped like a dolphin, war came.
At first, just like a spattering of hail
a voice of thunder…
then all smoke and fire and noise, that I didn’t understand.

It came across the playground.
It came into my teacher’s face.
It brought the roof down.
and turned my town to rubble.

I can’t say the words that tell you
about the blackened hole that had been my home.

All I can say is this:

war took everything

war took everyone

I was ragged, bloody, all alone.

I ran. Rode on the back of trucks, in buses;
walked over fields and roads and mountains,
in the cold and mud and rain;
on a boat that leaked and almost sank
and up a beach where babies lay face down in the sand.

I ran until I couldn’t run
until I reached a row of huts
and found a corner with a dirty blanket
and a door that rattled in the wind

But war had followed me.
It was underneath my skin,
behind my eyes,
and in my dreams.
It had taken possession of my heart.

I walked and walked to try and drive war out of myself,
to try and find a place it hadn’t reached.
But war was in the way that doors shut when I came down the street
It was in the way the people didn’t smile, and turned away.

I came to a school.
I looked in through the window.
They were learning all about volcanoes
And drawing birds and singing.

I went inside.
My footsteps echoed in the hall
I pushed the door and faces turned towards me
but the teacher didn’t smile.
She said, there is no room for you,
you see, there is no chair for you to sit on,
you have to go away.

And then I understood that war had got here too.

I turned around and went back to the hut, the corner and the blanket
and crawled inside.
It seemed that war had taken all the world and all the people in it.

The door banged.
I thought it was the wind.
But a child’s voice spoke
“I brought you this,” she said “so you can come to school.”
It was a chair. A chair for me to sit on and learn about volcanoes, frogs and singing
And drive the war out of my heart.

She smiled and said “My friends have brought theirs too, so all the children here can come to school”

Out of every hut a child came and we walked together,
on a road all lined with chairs.
Pushing back the war with every step.

Saturday, June 16, 2018

Clever tie-in to yesterday's post about Catherine of Aragon




Get it?

The first was created by Walt Disney, the second by Swedish actress Ingrid Bergman and Italian film director Roberto Rossellini. The second's full name is Isabella Fiorella Elettra Giovanna Rossellini Scorsese Wiedemann. The first's, oddly enough, is Ferdinand Fiorella Elettra Giovanna Rossellini Scorsese Wiedemann the Bull, or Ferdinand the Bull for short.

Okay, that last sentence may not be true.

More to be pitied than censured, I admit that this post may be not so much clever as irritating.

In the olden days I might have repented in sackcloth and ashes, but fortunately for me, the olden days are...


Irritating, yeah, that's the ticket.

Friday, June 15, 2018

Fun fact of the day


I'm sure many of you out there already know this, especially those of you from the British Commonwealth of Nations (kylie and Sue, I'm talking to you, and made a little rhyme besides), and most especially those of you ensconced in the United Kingdom itself, but I didn't know until today that Catherine of Aragon (pictured above), first wife of Henry VIII whom he divorced in order to marry Anne Boleyn, whom he eventually beheaded (Anne, not Catherine), was the daughter of none other than Ferdinand and Isabella, yes, that Ferdinand and Isabella, benefactors of one Cristoforo Columbo, Isabella I of Castile and Ferdinand II of Aragon, to be exact.

Catherine was betrothed at age 3 to the Prince of Wales, Henry's older brother Arthur, whom she eventually married but it was a short-lived marriage as Arthur died five months later. A few years later Catherine married Henry and became Queen Consort, the exact position in which Camilla Parker-Bowles Windsor-Mountbatten, Duchess of Cornwall, may find herself one day in the not-too-distant future, unless her husband Charles Philip Arthur George, Prince of Wales, should pre-decease his mother, the current reigning monarch, Elizabeth II, in which case she (Camilla, not Elizabeth) will not become Queen Consort but merely the Queen Stepmother, if they let her be Queen at all, which is doubtful.

The preceding paragraphs contain two of my longest sentences ever, but it simply cannot be helped. Well, it can, but what I have written, I have written. I am not in a mood to revise this morning.

It occurs to me that Camilla is more like Wallis Warfield Simpson, Duchess of Windsor, than Catherine of Aragon, being a divorcee and not a widow.

I love all things English except Yorkshire Pudding, whom I merely tolerate, and Mick Jagger. (I’m just pulling Yorkshire Pudding’s leg here; actually I rather like him. Why else would I have included a poem by him over there in the sidebar?)

A fun fact each day keeps the undertaker away.